1. Field of the Invention
The present invention relates to a marine gas cylinder apparatus.
2. Description of the Related Art
In conventional devices, as described in Japanese Patent Application Publication No. 3-1200 (patent publication 1), a marine gas cylinder apparatus includes a structure in which a cylinder block is connected to one of either a hull or a propulsion unit. A piston rod inserted into the cylinder block from a rod guide provided in the cylinder block is connected to the corresponding hull or propulsion unit. A piston rod side oil chamber in a side which receives the piston rod and a piston side oil chamber in a side which does not receive the piston rod are provided within the cylinder block. A gas chamber which communicates with the piston rod side oil chamber and the piston side oil chamber is integrally formed in the cylinder block, and a switching valve apparatus capable of switching a communication state among the piston rod side oil chamber, the piston side oil chamber and the gas chamber is provided in the cylinder block. It is possible to manually tilt up and down the propulsion unit easily while obtaining an assist force applying a gas pressure to the piston rod, by communicating the piston rod side oil chamber, the piston side oil chamber and the gas chamber, on the basis of an opening operation of the switching valve apparatus.
In the prior art in the patent publication 1, the switching valve apparatus is provided with a check valve which is closed by hydraulic pressure of the piston rod side oil chamber, in a communication passage, which communicates the gas chamber with the communication chamber and communicates the piston rod side oil chamber with the communication chamber. The switching valve apparatus is provided with a check valve which is closed by a hydraulic pressure of the piston side oil chamber, in a communication passage, which communicates the piston side oil chamber with the communication chamber. At this time, since the switching valve apparatus is structured such as to open and close each of the check valves by a pin supported to a valve case, it is necessary that the switching valve apparatus is provided with a support structure which can smoothly reciprocate without the pin falling down in the valve case, so that the structure becomes large and complex.
Further, in the prior art of the patent publication 1, the gas chamber is directly connected to the communication chamber. Accordingly, the gas cylinder apparatus has a free piston, which is arranged close to the piston, and an absorber valve and a return valve are provided in the piston. When a propulsion unit is collided with an obstacle and the piston and the piston rod are temporarily extended, the oil in the gas chamber opens the check valve so as to be supplied to the lower oil chamber of the free piston. The stop position of the free piston is thereby displaced before and after the collision. Accordingly, it is impossible to coincide a return position after absorbing an impact of the piston rod against the cylinder block with a tied position before absorbing the impact.